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Abstract:

A supercharging device for compressing charge air for an internal
combustion engine having a scroll compressor is proposed, a displacement
scroll (5) being connected to the supercharger shaft by way of an
eccentric arrangement between a front bearing and rear bearing of the
supercharger shaft (6), an externally driven drive element, such as a
belt pulley or the like, being provided outside a housing (1) of the
supercharging device, and the supercharger shaft (6) being connectable to
the externally driven drive element by means of a controllable clutch
member.
The intended distinguishing features of the supercharging device
according to the invention are a simpler bearing support and in
particular a front bearing of smaller dimensions. This is achieved in
that all connections of the drive and/or guide elements for the
displacement scroll are arranged between the front bearing (2) and the
rear bearing (3).

Claims:

1. A supercharging device for compressing charge air for an internal
combustion engine having a scroll compressor, a displacement scroll (5)
being connected to the supercharger shaft by way of an eccentric
arrangement between a front bearing and rear bearing of the supercharger
shaft (6), an externally driven drive element (9), such as a belt pulley
or the like, being provided outside a housing (1) of the supercharging
device, and the supercharger shaft (6) being connectable to the
externally driven drive element (9) by means of a controllable clutch
member (14), wherein all connections of the drive and/or guide elements
acting between the supercharger shaft (6) and the displacement scroll (5)
are arranged with the supercharger shaft between the front bearing (2)
and the rear bearing (3).

2. A supercharging device for compressing charge air for an internal
combustion engine having a scroll compressor, a displacement scroll (5)
being connected to the supercharger shaft (6) by way of an eccentric
arrangement between a front bearing (2) and a rear bearing (3) of the
supercharger shaft (6), an externally driven drive element (9), such as a
belt pulley or the like, being provided outside a housing (1) of the
supercharging device, and the supercharger shaft (6) being connectable to
the externally driven drive element (9) by means of a controllable clutch
member (14) by way of a carrier element (7) of the clutch member (14)
fixed to the supercharger shaft (6), wherein no force or torque
distribution is provided between the carrier element (7) of the clutch
member (14), fixed to the supercharger shaft (6), and the supercharger
shaft bearing (2) facing the carrier element (7).

3. The supercharging device as claimed in claim 1 or 2, wherein at one
end the displacement scroll is supported and guided via a mechanical
oscillating crank.

4. The supercharging device as claimed in one of the aforesaid claims,
wherein the drive element (9) is supported in a housing part (11) by
means of a bearing (13) independent of the supercharger shaft (6).

5. The supercharging device as claimed in one of the aforesaid claims,
wherein forces, in particular lateral forces, acting on the drive element
(9), can be dissipated to the supercharger housing (1) via the bearing
(13) of the drive element (9).

6. The device as claimed in one of the aforesaid claims, wherein a common
bearing (13) is provided for the drive element (9) and a clutch shaft
(10).

7. The device as claimed in one of the aforesaid claims, wherein the
drive element (9) is rotationally fixed to the clutch shaft (10) and is
supported by way of the clutch shaft (10).

8. The device as claimed in one of the aforesaid claims, wherein a
separately mountable housing part (11) is provided with the bearing (13)
for the drive element (9) and/or the clutch shaft (10).

9. The device as claimed in one of the aforesaid claims, wherein the
supercharger shaft (6) comprises at least one carrier disk (7), which
together with the controllable clutch member (14) forms a clutch.

10. The device as claimed in one of the aforesaid claims, wherein the
supercharger shaft (6) is supported in the supercharger housing (1)
separately from the clutch shaft (10) and the clutch member (14).

11. The device as claimed in one of the aforesaid claims, wherein all
components provided for actuation of the clutch are arranged and
supported on the controllable clutch member (14) side.

12. An internal combustion engine having a charge air compressor, wherein
a device according to one of the aforesaid claims is provided.

Description:

[0001] The invention relates to a supercharging device for compressing
charge air for an internal combustion engine according to the preamble of
claim 1.

[0002] Various supercharging devices for use on internal combustion
engines have been disclosed, such as so-called turbochargers, which are
driven by the exhaust gas flow from the engine. In addition there are
supercharging devices which work on the displacement principle. Machines
of the displacement type which have been disclosed also include devices
which function with a scroll compressor. In such a compressor a
displacement element is moved along a spiral housing. The displacement
element is generally also of a spiral shape and is driven by an eccentric
of a drive shaft. Supercharging devices with scroll compressors have been
described, for example, in the publications DE 10 2007 043 579 A1, DE 10
2007 043-595 B4, DE 26 03 462 or EP 0 899 423 A1. A supercharging device
having an oscillating crank bearing for the displacement scroll is
furthermore described in DE 10 2009 017 201 A1.

[0003] Such supercharging devices, which work on the displacement
principle, are generally mechanically coupled to a drive member of the
internal combustion engine. Internal combustion engines are usually
provided with a belt drive for auxiliary units, so that these are
integrated into such a belt drive by means of a belt pulley. The belt
drive exerts large lateral forces on the bearing shaft, so that its front
bearing facing the belt pulley has to be of correspondingly large
dimensions.

[0004] For flexible operation, supercharging devices that can be switched
via magnetic clutches have also been disclosed by the publications EP 0
557 598 B1 and EP 0 545 189 B1. The supercharging devices described in
this state of the art are provided with a further belt drive between the
clutch and the front bearing of the supercharger shaft facing the clutch,
in order to drive not only a first eccentric arrangement directly
connected to the supercharger shaft but also a second eccentric
arrangement for the displacement scroll. This additional belt drive again
imposes lateral forces on the supercharger shaft, which have implications
for the necessary dimensioning of the front bearing.

[0005] The object of the invention, therefore, is to develop a
supercharging device so as to simplify the bearing support and in
particular to reduce the dimensions of the front bearing.

[0006] Proceeding from a supercharging device according to the preamble of
claim 1, this object is achieved by the characterizing features of that
claim.

[0007] The measures specified in the dependent claims afford advantageous
embodiments and developments of the invention.

[0008] According to the invention all connections of the drive elements
and/or guide elements acting between the supercharger shaft and the
displacement scroll are now arranged between the front bearing and the
rear bearing.

[0009] In this way the part of the supercharger shaft pointing from the
front bearing to the clutch or external drive element is freed of all
lateral forces, which might be exerted by such drive and guide elements.
This serves, according to the invention, to simplify the bearing support
and in particular also the dimensioning of the front bearing.

[0010] The arrangement of all drive elements and guide elements of the
displacement scroll cited above afford a supercharging device, in which
no transfer gear elements for a force or torque split are provided
between a carrier element fixed to the supercharger shaft and the bearing
of the supercharger shaft pointing towards the carrier element. The free
end of the supercharger shaft with carrier element in the form of a
carrier disk, for example, is freely exposed virtually from the bearing
of the supercharger shaft adjacent to the carrier element. The fact that
no forces or torques of any kind of the supercharger shaft are split
between the carrier element and said bearing means that the possible
lateral forces cited above are avoided.

[0011] In a supercharging device according to the invention the
displacement scroll is guided on its second eccentric arrangement by an
oscillating crank, which through interaction with the first eccentric
arrangement ensures the required movement of the displacement scroll.
This type of oscillating crank used as a guide element affords positive
guidance without any so-called dead points. For such a positive guidance
of the displacement scroll it will suffice to drive this scroll via the
supercharger shaft and the eccentric arrangement situated on it.

[0012] In a preferred embodiment the controllable clutch member is
connected to the drive element by means of a clutch shaft. The drive
element, which may be a conventional belt pulley, for example, connects
this to the drive side of the clutch member via the clutch shaft.

[0013] Here the drive element is supported in a housing part of the
supercharging device by means of a bearing independent of the
supercharger shaft. This measure allows all forces that are transmitted
to the supercharging device via the drive element, for example the belt
pulley, to be dissipated directly into the housing of the supercharging
device without acting on the supercharger shaft. This is particularly
important particularly with regard to any lateral forces occurring. Since
in conventional internal combustion engines the belt drive, by way of the
belt pulleys, has to transmit a considerable torque to the auxiliary
units and in particular also to a supercharging device according to the
invention, such belt drives are subjected to a corresponding
pre-tensioning and through this pre-tensioning generate considerable
lateral forces.

[0014] The rotational speeds required of a supercharging device mean that
the belt pulley, at least in the case of a direct coupling into the belt
drive of the internal combustion engine, must not be of too large
dimensions, although for transmitting torque to a belt pulley this
results in small lever ratios, which have to be compensated for by
greater pre-tensioning in the belt drive in order to increase the
friction between the belt and the belt pulley. For design reasons,
therefore, the lateral forces referred to above cannot be avoided.

[0015] If the drive element is supported directly in a housing part of the
supercharging device, however, the lateral forces can be dissipated via
the housing, so that the supercharger shaft, which drives the
displacement element, is not adversely affected by such lateral forces.
This in turn allows a more compact design of the bearings for the
supercharger shaft provided inside the housing, so that a larger overall
space is available for the requisite displacement volume.

[0016] The clutch shaft of the controllable clutch member is preferably
also supported in a housing part independently of the supercharger shaft.
The controllable clutch member, which is advantageously rotatably
supported via the clutch shaft, may contain the substantial mass of the
entire clutch. The bearing for the clutch shaft therefore has to be
correspondingly designed and dimensioned. If this bearing is also
supported directly on a housing part, the bearing support of the
supercharger shaft will also remain unaffected by this measure. As a
result the interior space of the supercharger housing can in turn be
largely used to provide the corresponding displacement volume.

[0017] In a particularly advantageous embodiment a common bearing is
provided for the clutch shaft, for the controllable clutch member and for
the externally driven drive element. In this way it is possible, using
one single, common correspondingly stable bearing, for all forces, both
the lateral forces through the belt drive and the forces generated by the
high-mass parts of the controllable clutch member and the clutch shaft,
to be dissipated into the housing, without the bearing of the
supercharger shaft and of the displacement element connected thereto
being affected.

[0018] The housing part, which carries a bearing for the drive element
and/or the clutch shaft, is advantageously designed as a separately
mounted, flange-like component. This affords considerable advantages for
the production and assembly of a supercharging device according to the
invention. All forces occurring, which are applied to the flange-like
housing part by the accordingly stable bearing by way of the drive
element or the rotating parts of the controllable clutch member, can be
dissipated to the housing of the supercharging device by way of
corresponding bolted connections. In principle force-transmitting
connections, for example dowels, pins or the like, can also be provided
elsewhere between the housing and the flange-like housing part.

[0019] In a development of the invention the supercharger shaft is
provided with at least one carrier disk, on which the controllable clutch
member can act non-positively. In one particular embodiment the
non-positive connection is achieved by way of frictional connection, that
is to say the controllable clutch member comprises a disk, which is
designed with a frictional face to complement the carrier disk and which
in an axial direction of the supercharger shaft can be braced with the
carrier disk of the supercharger shaft. Where necessary, one or more
clutch plates may also be provided between them. The force may be
transmitted between the controllable clutch member and the supercharger
shaft in various ways according to known, conventional clutch mechanisms.
In principle a non-positive connection via a positively interlocking
coupling is also feasible, for example via a Hirth coupling or the like.
It is advantageous, however, if the supercharging device can be
selectively engaged with the drive element rotating, which in the case of
a frictional connection is possible without the interposition of other
torque converting elements.

[0020] As already mentioned above, in a supercharging device according to
the invention the supercharger shaft may be supported separately from the
clutch shaft and by and large from the clutch member. This bearing
support is preferably undertaken inside the supercharger housing.
Scroll-type superchargers are advantageously constructed so that they are
substantially symmetrical about a plane of symmetry running transversely
to the supercharger shaft. To this end scroll-type superchargers can be
designed so that the scroll housing for producing the displacement volume
is sub-divided by a partition wall lying in the plane of symmetry, a
spiral displacement element being moveably arranged on both sides of this
partition wall. This partition wall is provided with openings, so that
both sides of the scroll-type supercharger are fed from a common air
supply and discharge into a common outlet air line. This symmetrical
construction of a scroll-type supercharger allows the supercharger shaft
to be supported on both sides and in between allows an eccentric of the
supercharger shaft to be centrally supported in the area of the partition
wall.

[0021] If a supercharger according to the invention is now provided with a
clutch member, which keeps the supercharger shaft itself free of all
lateral forces and moreover also supports the greater proportion of the
high-mass parts of the clutch elsewhere, the bearings of the supercharger
shaft can also be kept compact using a controllable clutch and can
furthermore be of identical design on both sides of the supercharger
shaft.

[0022] Accordingly in an advantageous embodiment of the invention all
components provided for actuating the clutch are arranged and supported
on the controllable clutch member side, so that only one carrier element
required for transmitting the force, for example a carrier disk, is
provided on the supercharger shaft side. This carrier disk may be made
from correspondingly lightweight material, for example magnesium,
titanium, carbon or corresponding material.

[0023] One problem with a supercharging device for internal combustion
engines is that this device is generally subjected to a speed even
greater than that of the internal combustion engine. Speeds 2 to 3 times
greater than the speed of the internal combustion engine are quite
possible. The mechanism which has to ensure the smoothest possible
running of the scroll-type supercharger is correspondingly elaborate. In
order to cater for this mechanism and in particular also the balancing of
masses, it is therefore basically advantageous to make all moving parts
of such a supercharger of lightweight construction.

[0024] If according to the invention a corresponding supercharging device
is then provided with a clutch, this lightweight construction and the
fundamental construction of a conventional supercharger can be retained,
if all components, which by virtue of the clutch construction entail a
corresponding additional mass or which are subjected via the belt drive
to corresponding lateral forces, are supported directly on the housing or
on the housing part, without adversely affecting the supercharger shaft
and hence the internal construction of the supercharger.

[0025] An exemplary embodiment of the invention is represented in the
drawing and will be explained in more detail below with reference to the
figure.

[0026] In particular:

[0027] FIG. 1 shows a sectional representation of a scroll-type
supercharger without a clutch according to the invention,

[0028]FIG. 2 shows a detail of a scroll-type supercharger with a clutch
according to the invention, likewise in a sectional representation,

[0029]FIG. 3 shows a top view of an opened supercharging device in a
first operating position and

[0030] FIG. 4 shows a top view according to FIG. 3 in a second operating
position.

[0031] The supercharger housing 1 comprises two outer supercharger shaft
bearings 2, 3 and an eccentric bearing 4, which is arranged between them
and which serves for eccentrically guiding a displacement scroll 5, the
drive being provided by way of the supercharger shaft 6.

[0032] In the embodiment according to FIG. 1 it can be seen that the
supercharger shaft 6 carries a belt pulley 9. The supercharger shaft
bearing 2 is therefore of significantly larger dimensions and is designed
for considerably greater lateral forces than the opposing supercharger
shaft bearing 3. The supercharger shaft bearing 2 takes up a
correspondingly large overall space.

[0033] In the embodiment according to FIG. 2 with clutch according to the
invention the supercharger shaft 6 is provided with a carrier disk 7,
which has a friction face 8 in its outer area. Like all other moving
parts of the supercharging device, the carrier disk 7 may also be of
lightweight construction and in particular may also be produced from a
light metal.

[0034] According to the invention the supercharger shaft 6 is now no
longer driven directly by the belt pulley 9 in the belt drive of an
internal combustion engine.

[0035] Instead, the drive is provided by mounting the belt pulley 9 on a
clutch shaft 10, which is supported by way of a clutch bearing 13 in a
housing flange 11 with a bearing fitting 12. The housing flange 11 can be
firmly fixed to the housing 1 by bolted connections, not represented in
further detail.

[0036] On the side of the housing flange 11 facing the supercharger
housing 1, the clutch shaft 10 carries a controllable clutch member 14.
The clutch member 14 comprises a clutch disk 15 having a friction lining
16. The friction lining 16 enables the clutch disk 15 to drive the
carrier disk 7 with a corresponding frictional connection.

[0037] The frictional connection can be established in a manner not
further represented, for example also through the interposition of one or
more clutch plates. The clutch member is actuated by schematically
represented actuating members 17. The actuating members of the clutch
member 14 may be conventionally configured, for example.

[0038] The carrier disk 7 is preferably permanently braced with the clutch
disk 15, for example by means of spring pressure, and is actively
released by the actuating member. This can be achieved by a conventional
construction, for example with the aid of a disk spring, not further
represented. The clutch can then be disengaged by a corresponding,
controllable actuating member, for example a solenoid, a servomotor or
the like, it being possible to open the clutch through corresponding
counter-pressure to the biased spring.

[0039] An inverse construction is obviously also feasible, in which the
clutch is actively closed and passively opened.

[0040] The actual design of the clutch and its actuating members is of
subordinate importance in the present invention. Rather what is important
is that the major part of the high-mass clutch members and also the belt
pulley 9 be supported separately from the supercharger shaft 6, as is the
case in the exemplary embodiment shown, where it is supported via the
clutch bearing 13. This clutch bearing 13 can be of robust dimensions and
can be designed so that not only is the substantial mass of the clutch
supported but the lateral forces applied by the belt drive are at the
same time dissipated into the supercharger housing 1.

[0041] It can clearly be seen in the exemplary embodiment represented that
the free end of the supercharger shaft, which supports the carrier disk
7, does not have any transmission elements of any kind between the
carrier disk 7 and the bearing 2 facing the carrier disk 7, for
distributing the torque transmitted by the carrier disk.

[0042] It can be seen from FIGS. 3 and 4 that the charge air volume 18 is
moved as closed, lunate chambers in the rotation of the supercharging
device, thereby delivering and compressing the charge air.

[0043] The displacement scroll 5 is supported at the outer end in an
oscillating crank 19. The bearing axis 20 of the displacement scroll 5 is
forced into a periodically oscillating movement on a circular segment
through the positive guidance by the oscillating crank 19. The
oscillating crank 19 is rotatably supported in the oscillating crank axis
21 in the housing 1.

[0044] This oscillating bearing support of the displacement scroll 6 with
the oscillating crank 19 produces a positive guidance of the displacement
scroll 5 without dead points. The displacement scroll 5 is driven solely
via the supercharger shaft 6. All drive and guide elements for the
displacement scroll are arranged between the front bearing 2 and the rear
bearing 3.

[0045] On the side facing the clutch the supercharger shaft supports only
the carrier disk 7 for transmitting torque. This disk is stressed only in
an axial direction, however, and does not transmit lateral forces of any
kind.

[0046] This allows a correspondingly simpler, more compact and identical
configuration of the supercharger shaft bearings 2, 3. This affords a
larger space for the displacement volume.

[0047] Arranging the clutch bearing in a housing flange according to the
exemplary embodiment shown moreover facilitates assembly of the
supercharger clutch and affords good access in the case of repair and
servicing.